Membrane Cleaning Questions & Answers

How often should I clean my membranes?

In normal operation, the membrane in reverse osmosis membrane elements can
become fouled by suspended solids, microorganisms and mineral scale. These
deposits build up during operation and cause loss in water output or salt
rejection, or both. Membrane elements should be cleaned whenever the normalized
water output rate drops by 15% from its initial flow rate (the flow rate
established during the first 24 to 48 hours of operation) or when salt content
in in the product water rises noticeably.

It should be noted that the water output rate will drop if feedwater temperature
decreases (see Temperature Correction). This is normal and does not indicate
membrane fouling.

Is is necessary to heat our RO cleaning solution when the temperature of
our well water is already relatively warm and does not change much
throughout the year?

If your cleaning solution temperature is at
least 20 deg C, then you do not need a heating element. Also, as you
recycle the water there will be further rise in temperature, which
should be kept below 50 deg C.

What is the proper sequence to follow when cleaning my membranes?

Membrane Cleaning Sequence

Acid Cleaning

Flush

Alkaline
Cleaning

Flush

Sanitizing

Flush

What should the flow rate be for proper membrane cleaning?

Membrane Type

Medium Flow (MF)

High Flow (HF)

4" x 40"

4

10

4" Magnum

4

10

6" x 40"

12

20

8" x 40"

25

35

8" Magnum

25

35

Estimate of Total Flow Required for
Membrane Cleaning

HTF = NV × HF
MTF = NV × MF

HTF = High Total Flow

MTF = Medium Total Flow

NV = Number of Vessels in Parallel

HF = High Flow from Flow Table

MF = Medium Flow from Flow Table

How
much cleaning solution will I need to clean my membranes?

Membrane Type

Chemical Solution
Volume, Gallons (Vol)

4" x 40"

2.5

4" Magnum

3.5

6" x 40"

4.0

8" x 40"

6.0

8" Magnum

8.5

Estimate of Cleaning Solution Volume

V = El × Vol
× 5

El = Number of Elements

Vol = Volume of one element from Flow Tables

Which Membrane Cleaner Should I Use?

The membrane cleaner required will depend on the type of fouling the membrane
has been exposed to. Visit the below page to troubleshoot:Click Here

In Mongolia we are using RO elements Dow/Hydranautics BW30LE-4040,
treating groundwater high in TDS (no organics).
For CIP, can we use HCl as a cleaning agent? We do not have Cirtic Acid and shipping will take a long time
(getting through Chinese Border). If we can use HCl, what dosage or solution strength should we use?

Yes, you can use HCl. Add acid to water very slowly and carefully while stirring (mixing) till you have a pH of 3 (do not go below 2). Use this water and circulate for cleaning.